Hey there! The answer is:
386 milligrams
Step-by-step explanation:
To figure this out multiply 0.386 by 1000 because a milligram is 1000x bigger than a gram.
0.386 x 1000 = 386
Also, because it is 1000 times bigger, you can move the decimal over 3 places because there are 3 zeros in 1000.
Let me know if you have any questions! :)